Girls are not meant to have se.x/children when they are as young as 13. At that age, the female body is not even close to the end of puberty.

The right time to have se.x and become pregnant is when your body is physically capable of having a child. And, that is, when you're an adult.

A girl's body at that age is just simply too weak to give birth.

As for virginity issues and what not, I would suggest a vaccination for the human papillomavirus (HPV) which is the virus that causes cervical cancer. It can be caught by any means of sexual contact. And practice safe se.x. ALWAYS.